Rob, from the photo it appears that the dash is vinyl covered, based on texture and uneven appearance inside the hole. If so I suggest you look at the thickness of the molded ring around the clock hole on the backside, and also look at the inside edge, by pulling up the vinyl slightly. I suspect you may see signs of some machining to enlarge the hole. All it takes is to make it too large is 1/8" dia , or 1/16" around the inner edges. It looks to me that the PO enlarged it slightly to fit some non original item. I'll measure the outside dia of the back side ring on mine tonight, so we can compare.
Tom
Tom